1. Field of the Invention
The present invention relates to the use of ascorbic acid in combination with chemotherapeutic drugs to increase the inhibitory effects of the chemotherapy and to reduce its serious side effects and the use of ascorbic acid for radioprotection in radiotherapy.
2. The Prior Art
It is known that some types of cancer, such as lymphoblastic anemia, Hodgkin""s disease and testicular tumors respond very well to chemotherapy, which is constantly being improved. However, there are many types of cancer, some of them very widespread, which do not respond adequately to chemotherapy. Administration of chemotherapeutic agents is often associated with substantial side effects, such as loss of hair, nausea, vomiting, cardiomyopathy, bone marrow suppression, immunosuppression, hematopoietic dysfunction, leukopenia, etc. Therefore, there is a great demand for pharmaceutical drugs that increase the susceptibility of cancer cells to chemotherapeutic agents as well as drugs that mitigate or completely suppress the side effects observed with the use of chemotherapeutic agents as well as radiation therapy.
In addition, it is known from epidemiological studies that there is a close correlation between the vitamin C status and the incidence of certain types of tumors. Low plasma levels of vitamin C correlate closely with the risk of developing cancer of the esophagus, larynx, oral cavity, pancreas, stomach, rectum, breast and cervix. By reducing carcinogenic and mutagenic substances in the body, vitamin C has an important protective function. The preventive effect of vitamin C with respect to tumors of the gastrointestinal tract can be explained in part by the ability of the vitamin to prevent the formation of nitrosamines. It is also known that vitamin C is one of the most effective antioxidants in the human body. Free radicals are formed by endogenous metabolites and are induced by exogenous substances or radiation. Free radicals can damage proteins, enzymes, lipids and the genetic material. Studies on human blood plasma have shown that vitamin C is especially effective as protection against peroxy radicals. Water-soluble vitamin C regenerates (chemically reduces) oxidized vitamin E and thus provides additional protection for the lipid membranes.
One of the first studies of the use of vitamin C in cancer therapy was conducted by Cameron and Pauling. The group of volunteers included 100 terminal cancer patients who received 10 g of vitamin C orally each day. The control group consisted of 1000 patients receiving a comparable therapy without vitamin C. The survival time of the cancer patients treated with vitamin C was longer than that of the control group. E. Cameron, L. Pauling, Proc. Natl. Acad. Sci. USA 75,4538-42 (1978).
In addition, Cameron has described a therapeutic concept for treatment of cancer patients based on adjuvant, high-dose intravenous vitamin C therapy (0.5 to 10 g/day), followed by continuous oral doses of vitamin C (10 to 30 g). E. Cameron. Medical Hypotheses 36,190-194 (1991). The following effects of this therapy were described:
1. improvement in general well-being and the Karnofsky scale,
2. relief from pain in cases of skeletal metastasis,
3. decline in protein tumor markers in the serum,
4. in favorable cases, absorption of malignant pleural effusions and a reduction in the size of pulmonary metastases.
E. Cameron; Medical Hypotheses 36, 190-194 (1991)
In addition, there are examples of cases in the literature where an improvement in general condition and spontaneous remissions have been described in conjunction with high-dose vitamin C therapy in cancer patients. H. D. Riordan J. A. Jackson, M. J. Schultz. Orthomolecular Med. 5 (1), 5-7 (1990); A. Campbell, T. Jack, E. Cameron. Oncology 48 (6) 495-497 (1991).
The positive findings by Cameron and Pauling E. Cameron, L. Pauling, Proc. Natl. Acad Sci. USA 75, 4538-42 (1978) were not confirmed subsequently in some cases, but in vitro tests on cell lines have indicated that vitamin C in certain concentrations has a cytotoxic effect on tumor cell lines. However, findings obtained on cell cultures cannot readily be applied to in vivo conditions. Nevertheless, it can be regarded as confirmed that vitamin C in certain concentrations has a cytotoxic effect on tumor cell lines. The growth of normal cell lines is therefore not influenced in these concentrations. Thus, vitamin C has a differentiated effect on the growth of neoplastic cell lines and normal cell lines. Whether vitamin C is a therapeutic agent with a cytotoxic effect on tumor cells cannot yet be decided on the basis of research results available so far.
More important than the cytotoxic potential of vitamin C on tumor cells is the effect of this vitamin on the entire body which has been weakened by the cancer process. Vitamin C increases the body""s defense mechanisms in various ways. This affects both the cellular and humoral immune response of the body. Vitamin C stimulates lymphocytic blastogenesis and promotes the mobility and chemotaxis of neutrophils, eosinophils and monocytes, and leads to definite improvement in the blood picture by stabilizing platelet count and white blood cell count despite concomitant chemotherapy. In the area of the humoral immune response, high doses of vitamin C lead to increased antibody production and stimulate phagocytosis.
Vitamin C even increases the immune response in the presence of carcinogens such as dibutylamine and sodium nitrite as substance that produce nitrosamines, which normally lead to suppression of the cellular and humoral immune response. In addition to strengthening the immune system, vitamin C is also indispensable for the integrity of the membrane and the stability of the connective tissue. In addition, pain is diminished, especially in cases of skeletal metastasis, and side effects such as nausea and vomiting are reduced.
It has already been observed that enteral nutrition is often disturbed with regard to quantity and absorption during chemotherapy and radiation therapy. This applies in particular to the antioxidant vitamins alpha-tocopherol, beta-carotene and ascorbic acid. At the same time, however, the intracellular antioxidant potential is often reduced by cytostatics. It can be assumed that the cytotoxic effect of the anthracyclines, mitomycin and etoposide, in particular, is attributable in large part to the formation of aggressive radicals. The consequences of these oxidative processes induced by chemotherapeutic drugs are damage to membranes, proteins, enzymes and genetic material.
To determine whether antioxidant vitamin supplements can compensate for this loss, a study has already been conducted on 22 patients. These patients received daily oral doses of 825 mg DL-alpha-tocopherol, 45 mg beta-carotene and 450 mg ascorbic acid three weeks before the start of chemotherapy and radiation therapy. In addition to definitely reduced lipid peroxide concentrations in the blood, signs of reduced hepatotoxicity of the chemotherapy were observed in the patients receiving such supplements M. R. Clemens. Therapeutiische Rundschau, Volume 51, 483-488, 1994. However, it has been impossible to determine from this the influence of orally administered antioxidant vitamins on the antineoplastic effect of chemotherapy and radiation therapy and whether the side effects thereof are reduced in this way. Since absorption after oral administration may also be impaired during chemotherapy and radiation therapy, these experiments do not permit any conclusions regarding the effects of parenteral administration of high doses of vitamin C preparations over a period of several weeks.
It has now been discovered that ascorbic acid or its physiologically acceptable salts greatly improve the success of chemotherapy and radiation therapy while reducing their side effects when administered parenterally in a dose of more than 5 g as an adjuvant to chemotherapy or radiation therapy. In general, ascorbic acid or its salts are used in an amount of 5.0 to 30.0 g, preferably in an amount of 5.0 to 10.0 g. The parenteral preparation should have a pH between 6.0 and 8.0. As a result, an increase in the inhibitory effects of the chemotherapeutic drug and a tissue-protective effect in radiation therapy as well as a reduction in the sometimes very serious side effects have been observed. This surprising synergism occurs in vitro with a combination of a vitamin C therapy with such chemotherapeutic drugs as adriamycin, bleomycin sulfate, mitomycin C, methotrexate, vincristine sulfate, 5-fluorouracil, paclitaxel, doxorubicin and cisplatin. In animal experiments, a prolonged survival time was demonstrated with the combination with adriamycin.